1. Field of the Invention
The invention relates to a method for operating a geolocation database and to a geolocation database system.
2. Description of Related Art
The future usage of radio frequencies will encompass so called white spaces, e.g., regions in the frequency range from 110 MHz to 790 MHz for TV white space. Those white spaces are geographical regions in which licensed frequency bands may be used by license-exempt users, given the latter are certified and do not harm licensed users (opportunistic operation). A licensed user is also termed as an incumbent spectrum user—a spectrum user (usually a wireless communication system) that is licensed and certified by an authority, and is authorized to use a specified (e.g., allotted) frequency spectrum as a priority user. White spaces can have a temporal restriction, too.
For such usage, legislative regulation envisions—e.g., privately operated—databases (geolocation databases) which store (e.g., EU-wide) position data and transmission characteristics of known radio masts (or other devices which need protection from interferences), and which assume, based on radio propagation models, if signals of licensed users propagate to a given location at which, in consequence, interference-free reception has to be guaranteed.
When a license-exempt user wishes to transmit “in the white space”, it has to register with the geolocation database, providing his position and in particular the spectrum usage characteristics (e.g., if it is a fixed stationary or a mobile device), in order to obtain a permission (or having the permission denied).
For this decision process a terrain model and a radio propagation model estimating the radio environment at the position of the license-exempt user are used in order to determine the region where the non-licensed user might act (from the perspective of the incumbent user) as an interferer.
Only if no interference is expected, permission for transmission is granted to the license-exempt user.
As it is impossible to characterize the radio propagation and the associated interference with 100% accuracy for a given point in time and space (i.e., the spatial-temporal location), this decision process employs approximation models.
In addition to the up-to-dateness of the database, this accuracy impacts the decision if a license-exempt or non-licensed user obtains a permission to transmit.
It can be assumed that the terrain and radio propagation models used for protecting the incumbent users approximate the interference and deny license-exempt users the transmission in a way that a considerable part of white space resources is not used optimally. Depending on the business model for assigning and distributing usage rights of white spaces by license-exempt users, such sub-optimal usage results in financial losses.
Apart from the mentioned causes for the limited accuracy of the database approach, current means of using the database are generally not applicable for mobile frequency users—according to the current state of the art, such users had to re-register approximately every 60 seconds according to local regulations.
The worldwide introduction of geolocation databases as described above is planned in the form of distributed regional databases. Accordingly, improvements of this structure will be introduced by adding functionality via external components not changing the existing, internal architecture. The described embodiments are in principle independent of the internal structure of the geolocation database, as long as the known interfaces provide the functionality as described below.